1. Field of the Invention
This invention relates to a mowing machine, and more particularly, to a mowing machine including a motor provided on a vehicle body on which a weeding rotary body having on the outer circumference thereof a plurality of recessed-blade-carrying mowing plates is rotatably supported, and further including both a structure for removing the weeds which become entangled in a rotary weeding body while it is turned and a structure for simultaneously replacing the plurality of recessed-blade-carrying mowing plates by another set of object plates.
2. Description of the Related Art
In the past it has been preferable to mow and grade simultaneously but plain mowing plates could not be used for very long because they are easily broken. It is not useful to grade more soil than is necessary by a large machine provided with a plurality of thick blades. International Patent Application PCT/JP, 89/01206, proposed by MASARU TSUDA, discloses one conventional apparatus which shows the reformation of plain blades which are easily damaged.
Since the operational speed of this prior art weeder is set to a low level which does not allow the lawn grass to be cut, the weeding is performed with a very small quantity of broken pieces of lawn grass and broken pieces of hardskin-carrying weeds left adhering to the edges of the weeder.
As a result, the uncut lawn grass impinging upon the mass of the cut lawn grass and weeds adhering to the blades of the weeder is thereby repulsed or slips thereon, and does not even directly touch these blades, and the quantity of the broken pieces of lawn grass and weeds adhering to and winding around the blades tends to increase over time. This makes it necessary to interrupt the weeding operation and remove the grass adhering to the weeding plates and rotary weeding body.
Besides, the aforesaid front edges which serve to maintain the recessed blades sharp are dull, so that the weeding performed near the position of the projections is not as completely performed as near the location of the recessed blades.
Therefor, to more effectively carry out weeding, it has become necessary to adjust the rotational phase of a plurality of recessed blades so as to make it possible to sweep over a predetermined range in the rotating outer circumferential area of a weeding rotary body without permitting a gap in coverage.
If the recessed blades are excessively positioned on the rear side with respect to the front edges, the leaves and stalks of lawn grass come in a bunch into the clearances in front of the recessed blades and among the projections, so that the weeds on the front side thereof are protected by these leaves and stalks and left uncut.
Conversely, if the recessed blades are excessively positioned on the front side, even the projecting portions of solid objects, the sizes of which are larger than the distance between two adjacent projections, crash directly into the sharp recessed blades in many cases.
Therefore the recessed blades are easily damaged, and it becomes difficult to maintain the sharpness of the back blades.
Moreover, if the projections are formed to have a small length, the effect thereof in loosing the entangled weeds on a lawn decreases, and such projections lose effectiveness in catching a thick and hard stalk of a weed, which is often encountered on a lawn, and floating its root.
In addition, a preferable operation speed of the rotary weeding body in this prior art apparatus is not clearly defined.
According to these proposed techniques, the height at which the weeds are mowed is regulated mainly by varying the distance between a support shaft and the mowing plates in the structure of the rotary weeding body.
In order to wash or polish this apparatus, it is necessary that the rotary weeding body be removed with the support shaft from an apparatus body, or that the mowing plates may be removed one by one.
Namely, it is inconvenient to subject the apparatus to a washing or polishing operation.
The above-mentioned patent application does not include a proposal for providing a multifunction weeder, for example, a weeder having a plurality of types of weeding plates from which weeding plates having suitable types of blades are selected in accordance with the conditions at the job site.
There exist lawn mowers and grass cutters having mowing plates formed in a circle. Since these apparatuses have no function of selectively mowing types of grass softer than lawn grass, they are not the same kind of apparatuses as the apparatus disclosed in the above publication. In short, there are no concrete proposals for employing the techniques, in a lawn mower and a grass cutter, for attaching and detaching a plurality of grass cutting plates simultaneously to and from a rotary mowing body or removing entangled grass from the grass mowing plates while the rotary weeding body is turned.
The reasons for the above reside in the following.
Out of the blades and stalks of various kinds of grass, those of lawn grass are generally the thinnest and most flexible but they have a hard skin and are difficult to mow.
Therefore, when lawn grass impinges directly upon a mowing blade moving at a high speed, it presses the cut weeds and lawn grass which have already adhered to the front end portion of the blades and cuts and rubs them off before the lawn grass impinging upon the mowing blades has been cut off.
Such action occurs continuously while a rotary weeding body is rotated so that the cut weeds and lawn grass adhering to and wound around the mowing blades can be ignored while the mowing blades are sharp, i.e., and effective.
If such action appears on a rotary weeding machine, the mowing plate is easily broken because it is supported on a narrow center part.
Devices having blades similar to that of the blades on the weeding plates used in the present invention include a hedge trimmer used mainly for cutting off the twigs of a tree, and a miniaturized hedge trimmer used for mowing the grass in a small area.
Namely, the apparatus disclosed in PCT/JP, 89/01206 and the machine for removing weeds in lawns according to the present invention do not have any general points in common with any other types of grass cutters, lawn mowers and hedge trimmers regarding the function, operation, effect and objects thereof.